Aromatic thermoplastic polymers, including aromatic polycarbonate based compositions are known for their excellent properties in terms of transparency, heat resistance, and mechanical strength. Fogging of the surface of articles prepared from the thermoplastic polymers creates problems for many end-use applications, such as goggles/lenses or greenhouse panels, where the formation of condensed water beads on the surface thereby reducing transparency.
To reduce or eliminate fog on the surface of polycarbonate or other thermoplastic articles, anti-fog coatings have been developed. However, as the anti-fog coatings must be applied to the surface of the article, their use is less convenient and more expensive than having an anti-fog feature in the as-molded article.
The use of anti-fog additives for certain thermoplastics is known, for example, there are known anti-fog additives for polyethylene and poly(vinyl chloride). These additives include sorbitan esters, ethoxylated sorbitan esters, polyol esters and glycerol esters. Such additives present in the polyethylene and poly(vinyl chloride) material results in fog resistant articles made from such materials. Such additives allow for the elimination of anti-fog coatings. While these additives are known to be surface active and impart anti-fog properties to polyethylene and poly(vinyl chloride), they are unsuitable for polycarbonate and other aromatic thermoplastic polymers. These additives suffer from low thermal stability or are incompatible with the resin thereby preventing them from being effective anti-fog additives for aromatic thermoplastic polymers, especially polycarbonate.
Accordingly, although there are anti-fog coatings for polycarbonate and other aromatic thermoplastic polymers, there remains a need for anti-fog additives and/or methods of rendering such polymers fog resistant without the use of an anti-fog coating.